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Ascorbic Acid Content Varies among Baby Leaves and over the Season

Study of ascorbic acid and dehydro ascorbic acid levels in different leafy vegetables at different times of the year.

Year of Publication2011

Ascorbic acid (AsA) is one of the main antioxidants found in leafy vegetables. The total amount and proportion of the oxidised form dehydro ascorbic acid (DHA), could potentially be a parameter giving an indication of the stress level of the leaves. The assumption is that the higher the content of AsA and the lower the proportion of DHA, the better the shelf life potential. Three different studies were performed with a range of leafy salad vegetables to establish base levels of AsA and DHA that can be used as reference values for further studies. I. Commercially grown leaves of spinach (Spinacia oleracea), red chard (Beta vulgaris), pea shoots (Pisum sativum), rocket (Eruca sativa) and lambs lettuce (Valerianella locusta) were bought from a supermarket and were analysed. II. Commercially grown baby leaf spinach leaves (Spinacia oleracea) were analysed monthly over a time span of one year. III. Twelve different spinach cultivars (Spinacia oleracea) and Perpetual spinach beet (Beta vulgaris) were grown under glass house conditions and analysed. AsA and DHA concentrations were determined by HPLC. The general conclusion is that both AsA and DHA concentrations vary significantly between cultivars, between species and during the year. The studies demonstrated that total AsA+DHA content of a range of baby leaves ranged from 20-150 mg kg-1 fw, with significant difference in the proportion of DHA. The highest total concentrations in commercially grown spinach were found in the late autumn / winter / early spring season (250 - 350 mg kg-1 fw). The lowest concentrations were found in late summer season spinach (50 mg kg-1 fw). A large difference in total AsA+DHA content was observed among glasshouse grown spinach cultivars, in the range from 200-600 mg kg-1 fw with significant differences in the proportion of DHA. In conclusion these findings emphasise the difficulty of comparing studies performed with different crops at different times of the year.